User experience is about helping the user to accomplish their goals in the fastest and easiest way possible. On social media, the key is allowing users to navigate content quickly and easily, so they can interact with that content.
Below are two suggestions for gestures to navigate upwards, back to the higher-level mosaic view, which is currently only possible by clicking the back button.
The first suggestion (left) is to be able to scroll up from the top photo. This interaction is similar to pinterest or the "related images" section of google images.
The second suggestion (right) is to be able to pinch to zoom out from the column view to reach the mosaic. This would emphasize the fact that the former is contained within the latter.
Screenshots and sketches of the mosaic album view (left) and the column image view (right)
Here are the preliminary sketches I made from screenshots I took of a recent album I published from my trip to NYC.
In order to measure whether or not this gesture is useful, it should be tested for usage. Visual cues could be experimented with to educate users about the new feature.
I know this gesture would be useful and magical for me, but that's not the intent. The intent is that it's useful and magical for millions of users.
Some more sketches
Not really pertinent to the idea itself, but I thought it was pretty enough to share. Just sketching the thumbnail within a manually-calculated 16:9 grid, since my notes app doesn't support creating shapes with manually defined properties such as length and width.